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The atomic bomb, seven decades on

Next week marks the 70th anniversary of the detonation of the atomic bomb over Hiroshima, on 6 August 1945

How many were killed at Hiroshima?

Nobody knows exactly. With the fires and chaos that followed the explosion, there was no accurate death toll: early estimates varied from 8,000 to 100,000. Thousands fled their homes but died later, of burns, blood poisoning and radiation sickness. In late 1945, a government count based on casualty lists and neighbourhood surveys, concluded that 130,000 had died. A similar survey put the death toll in Nagasaki, bombed three days later, at between 60,000 and 74,000 (the force of the explosion was contained by steep hills). However, doctors and scientists found increased rates of leukaemia, cancer and cataracts in both cities until well into the 1970s.

Was the attack totally unexpected?

Yes. While the idea of an atomic bomb was known to Japan’s top brass and civilian leadership – a German submarine captured in May 1945 was on its way to deliver uranium ore to Japan’s own fledgling nuclear programme – they had no idea that the US had a finished bomb. In the spring of 1945, US secretary of war Henry Stimson debated with scientists working on the “Manhattan Project” about whether some warning of the bomb’s power could be given to the Japanese. It was decided not to, since the main priority was to use the bomb “to make a profound psychological impression on as many of the inhabitants as possible”.

Why was there any doubt it might not?

By that stage in the War, “area bombing” by the Allies in Germany and Japan was already resulting in a vast death toll. (On 9 March, 100,000 people died in a single fire-bombing raid on Tokyo; another 66 cities had been partially destroyed in daily, massive attacks.) Stimson felt Japan had been “so thoroughly bombed” the new weapon might not have “a fair background to show its strength”. He needn’t have worried. At 8.16am on 6 August, people in Hiroshima saw a single B-29 bomber flying high over the city. “The voice of our teacher saying: ‘Oh, there’s a B’, made us look up at the sky,” one student recalled. “In an instant we were blinded and everything was just a frenzy of delirium.” Announcing Japan’s surrender on 15 August, Emperor Hirohito spoke of a “new and most cruel bomb, the power of which to do damage is, indeed, incalculable”. Its power terrified the makers of the bomb too.

What did they fear?

Well before Hiroshima, the Manhattan Project scientists could see the danger of a new global order based on nuclear weapons, in which more and more nations would be competing to acquire one. In early 1944, Niels Bohr, a Danish physicist and Nobel laureate, shuttled between Washington and London, trying to persuade the Allies to let the USSR share in the development of the bomb in order to prepare “an international control scheme” for after the War – but to no avail. In August 1949, assisted by Klaus Fuchs, a German scientist (later convicted for giving the Russians stolen plans, including those of the Nagasaki bomb), the Soviet Union detonated its first nuclear device, in Kazakhstan. The UK was next, in 1952, followed by France in 1960. By the time China exploded its first bomb, in 1964, the US had some 30,000 warheads.

Have we come close to nuclear war?

The nearest the world came was the Cuban Missile Crisis of 1962, when President Kennedy sent 23 nuclear-armed B-52s to within striking distance of the Soviet Union – a final throw of the dice in his, successful, bid to persuade the Soviets to remove the nuclear-armed missiles they’d installed in Cuba, just 90 miles off US shores. However, across the decades of Cold War bomb-building, the closest we’ve come to another Hiroshima has probably been through accidents (see box) – a danger that increases with the number of nuclear warheads.

When was the number of nuclear warheads at its peak?

In 1985, on the eve of disarmament talks between Ronald Reagan and Mikhail Gorbachev, when the US and the USSR had more than 60,000 between them. By that point Pakistan had tested its first nuclear bomb (in 1983) and India, Israel and South Africa had joined the original nuclear club of Russia, the US, the UK, France and China (still the five permanent members of the UN Security Council). All this despite the Nuclear Non-Proliferation Treaty, introduced in 1968. Since then, however, the international effort to limit the spread of nuclear weapons, and dismantle those that exist, has borne fruit. The US, Russia and the UK have all more or less halved their nuclear stockpiles; South Africa and a handful of ex-Soviet nations renounced their nuclear arms programmes in the early 1990s. The number of nuclear warheads worldwide has fallen to around 17,000. Only nuclear rivals India, and Pakistan, along with China, Israel and renegade North Korea, have continued to add to their arsenals since the mid-1980s.

And has that all been due to international diplomacy?

No. Luck and force majeure have played their part, too. Back in 2003, Libya’s Colonel Gaddafi, alarmed by the allied invasion of Iraq, agreed to dismantle his nuclear programme – a very fortunate decision given Libya’s subsequent descent into anarchy. (By contrast Ukraine, which in 1994 gave up 2,000 nuclear warheads, may now wonder if that was such a good idea, given Russia’s behaviour since 2013.) Israel, which neither confirms nor denies the existence of its own programme, has probably been the most active inhibitor of other nations’ nuclear ambitions. In 2007, Israeli jets destroyed Syria’s main nuclear weapons plant – disguised as a Byzantine fort – at al-Kibar (again very fortunate, given the current civil war); and its spies are thought to have helped bring Tehran to the negotiating table by conducting an assassination programme against Iranian nuclear scientists, killing at least five in recent years.

Bombs away… accidents will happen

On 23 January 1961, three days after John F. Kennedy’s inaugural address, a B-52 Stratofortress was on a routine night patrol over the US eastern seaboard. All of a sudden, it suffered a major misfunction, its right wing sheered off, and its two hydrogen bombs, each 260 times more powerful than the Hiroshima bomb, came loose and fell on North Carolina. One slammed into a field, the other was caught in a tree. A secret military report found that on one bomb, three out of four safety mechanisms had failed. “One simple, dynamo-technology, low-voltage switch,” it concluded, “stood between the US and a major catastrophe.”

In a six-year investigation into the safety of US nuclear weapons, journalist Eric Schlosser found there were more than 1,000 accidents between 1950 and 1968. We’re far better “at creating complex technological systems than at controlling them”, he said. At 2.30am on 3 June 1980, former US national security adviser Zbigniew Brzezinski was woken by a phone call telling him 220 Soviet missiles had been launched at the US. Asking for confirmation, Brzezinski was told the correct figure was 2,200. Minutes later, he was told it was a false alarm. Investigations found that a computer chip worth 46 cents had failed. Brzezinski never woke his wife, “reckoning”, said ex-US defence secretary Robert Gates, “that everyone would be dead in half an hour”.